Question

The **concentration of vacancies** in niobium (Nb)
at 765˚C is 9.836 x 10^{18} cm^{-3}. If niobium has
a BCC crystal structure and a lattice parameter of 0.3302 nm,
**calculate the energy for vacancy formation** in
niobium.

Answer #1

Niobium (Nb) has an atomic radius of 0.1430 nm and a density of
8.57 g/cm^3. Determine whether it has an FCC or a BCC crystal
structure.

Niobium (Nb) has an atomic radios of 0.1430 nm and a density of
8.57 g/cm^3. Determine whether it has an FCC or a BCC crystal
structure.

Compute the concentration (number density, count per volume) of
vacancies in copper at room temperature if the lattice parameter of
FCC copper is 0.3615 nm at room temperature (25oC, 298 K),
and the activation energy to form a single vacancy is 0.9 eV.
Use 8.617x10-5 eV/(atom-K), exactly, as Boltzmann's Constant.
Note: You could look up the density and atomic weight of copper
to compute the intermediate value of atom concentration you need
for this problem.
But here I give you...

--Given Values--
Atomic Radius (nm) = 0.116
FCC Metal = Gold
BCC Metal: = Sodium
Temperature ( C ) = 1017
Metal A = Tin
Equilibrium Number of Vacancies (m-3) = 6.02E+23
Temperature for Metal A = 369
Metal B = Gallium
1) If the atomic radius of a metal is the value shown above and it
has the face-centered cubic crystal structure, calculate the volume
of its unit cell in nm3? Write your answers in
Engineering Notation.
...

A Si sample with ND=1x10^17 cm^-3 has a steady state excess hole
concentration maintained at x=0 of 1x10^16 cm^–3. Assume the
electric field is zero, ni=1.5x10^10 cm^–3, μn=800 cm^2 /Vs, μp
=200cm^2 /Vs, τ n = τ p =10μs, T=300K.
A) Plot the hole concentration as a function of distance x into
the material, for x=0 to 3 x Lp
B) What is the quasi-fermi level separation at x=50μm?
C) Calculate and plot the diffusion current density as a
function...

Consider a silicon crystal that has been doped with 4 x 1016
cm-3 boron atoms and 9 x 1015 cm-3 phosphorous atoms. (a) What is
the overall charge of the silicon? (b) Is the material n-type or
p-type? Explain. (c) What are the equilibrium electron and hole
concentrations at room temperature (300K)? (d) What is the ionized
donor density in the crystal? (e) What is the neutral donor density
in the crystal? (f) Now assume the sample is heated to...

The thermal expansion of aluminum is plotted against temperature
in the figure below. Measure the plot at 800 K and see how well the
result compares with the data in the table below. (a) (b) (a) The
overall thermal expansion (ΔL>L) of aluminum is measurably
greater than the lattice parameter expansion (Δa>a) at high
temperatures because vacancies are produced by thermal agitation.
(b) A semilog (Arrhenius-type) plot of ln (vacancy concentration)
versus 1/T based on the data of part (a)....

a.If a solution of a compound that has a molar absorptivity 45
M–1 cm–1 placed in a cuvette with a path length of 10 mm has an
absorbance of 0.65, what is the molarity of the compound in
solution? Show work.
b. What would the value of the equilibrium constant be for the
formation of FeNCS2+ from Fe3+ and SCN– , if the final equilibrium
concentration of [FeNCS2+] = 7.84 x 10–3 M when the solution
initially had [Fe3+] =...

1)At 25°C, some second-order reaction 3 X
(g)→ 2 Y (g) + Z
(g) has a half-life of 5.82 hours when the
initial concentration of X is 4.46 M.
(a) What is rate constant for this reaction?
(b) How much X will be left after
17.5 hours?
Example of answer: (a)
k = [type
your answer] M–1 h–1;
(b) [X]t =
[type your answer] M.
2)
For some second-order reaction: 3 X
(g)→ Y (g) + Z
(g).
The following...

1) Describe an example of each of the following that may be
found of your kitchen: Explain how your choice falls into this
category, and if there is a chemical name or symbol for it, provide
that as well. Provide a photo of your example with your ID card in
it. a) a compound b) a heterogeneous mixture c) an element (symbol)
Moving to the Caves… Lechuguilla Caves specifically. Check out this
picture of crystals of gypsum left behind in...

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